There are available to the consumer an ever-increasing number of portable battery operated devices which create an ever-increasing demand for batteries to serve as power sources. Conventionally, primary batteries such as LeClanche' carbon-zinc, zinc chloride or alkaline batteries have been used as power sources in many applications including consumer products. However, these primary batteries are typically not designed for recharging, and they must be replaced with new batteries as the old ones are drained.
Nickel-cadmium batteries, which can repeatedly be recharged and reused for a significant number of charge/discharge cycles, are now available to replace most common primary batteries. Such nickel-cadmium batteries may be made with terminals and case configurations and sizes identical to primary batteries so as to be usable in the relatively large number of products designed for primary batteries. Nickel-cadmium batteries may also be associated with battery chargers for providing energy to recharge the nickel-cadmium batteries. By providing chargers for nickel-cadmium batteries having the same size and shape configuration as primary batteries, there is a risk that a consumer may insert primary batteries into the charger, even though such primary batteries are not intended to be recharged. Many primary batteries, if subjected to charging current, will eventually release electrolyte which can corrode and damage the product in which the battery resides. Charging of such primary batteries may also produce other adverse effects.
In prior art approaches, in order to provide for charging of nickel-cadmium batteries while avoiding the adverse effects associated with recharging primary batteries, the nickel-cadmium batteries have been made of special size or shape to distinguish them from the non-rechargeable or primary batteries so that only the rechargeable battery will physically fit into a charger for recharging. Other prior art approaches have provided the rechargeable battery with a third contact terminal (in addition to the two contact terminals used to discharge energy from the battery) which is used to charge the battery. A non-rechargeable battery not having the third charging contact terminal cannot be charged in the charger. Another prior art approach provides for the insertion of a uni-directional current flow device into the non-rechargeable battery so that current may flow from the battery during discharge but cannot flow through the battery in the reverse direction during charging. Each of these prior art approaches has not proved to be entirely satisfactory at least for the reason that they each involve additional or special parts or components and hence increase the cost of the battery.